An Italian experiment has unveiled evidence that fundamental particles known as neutrinos can travel faster than light. Other researchers are cautious about the result, but if it stands further scrutiny, the finding would overturn the most fundamental rule of modern physics — that nothing travels faster than 299,792,458 metres per second.
The experiment is called OPERA (Oscillation Project with Emulsion-tRacking Apparatus), and lies 1,400 metres underground in the Gran Sasso National Laboratory in Italy. It is designed to study a beam of neutrinos coming from CERN, Europe’s premier high-energy physics laboratory located 730 kilometres away near Geneva, Switzerland. Neutrinos are fundamental particles that are electrically neutral, rarely interact with other matter, and have a vanishingly small mass. But they are all around us — the Sun produces so many neutrinos as a by-product of nuclear reactions that many billions pass through your eye every second.
The 1,800-tonne OPERA detector is a complex array of electronics and photographic emulsion plates, but the new result is simple — the neutrinos are arriving 60 nanoseconds faster than the speed of light allows. “We are shocked,” says Antonio Ereditato, a physicist at the University of Bern in Switzerland and OPERA’s spokesman.
Breaking the law
The idea that nothing can travel faster than light in a vacuum is the cornerstone of Albert Einstein’s special theory of relativity, which itself forms the foundation of modern physics. If neutrinos are travelling faster than light speed, then one of the most fundamental assumptions of science — that the rules of physics are the same for all observers — would be invalidated. “If it’s true, then it’s truly extraordinary,” says John Ellis, a theoretical physicist at CERN.
Ereditato says that he is confident enough in the new result to make it public. The researchers claim to have measured the 730-kilometre trip between CERN and its detector to within 20 centimetres. They can measure the time of the trip to within 10 nanoseconds, and they have seen the effect in more than 16,000 events measured over the past two years. Given all this, they believe the result has a significance of six-sigma — the physicists’ way of saying it is certainly correct. The group will present their results tomorrow at CERN, and a preprint of their results will be posted on the physics website ArXiv.org.
At least one other experiment has seen a similar effect before, albeit with a much lower confidence level. In 2007, the Main Injector Neutrino Oscillation Search (MINOS) experiment in Minnesota saw neutrinos from the particle-physics facility Fermilab in Illinois arriving slightly ahead of schedule. At the time, the MINOS team downplayed the result, in part because there was too much uncertainty in the detector’s exact position to be sure of its significance, says Jenny Thomas, a spokeswoman for the experiment. Thomas says that MINOS was already planning more accurate follow-up experiments before the latest OPERA result. “I’m hoping that we could get that going and make a measurement in a year or two,” she says.
If MINOS were to confirm OPERA’s find, the consequences would be enormous. “If you give up the speed of light, then the construction of special relativity falls down,” says Antonino Zichichi, a theoretical physicist and emeritus professor at the University of Bologna, Italy. Zichichi speculates that the ‘superluminal’ neutrinos detected by OPERA could be slipping through extra dimensions in space, as predicted by theories such as string theory.
Ellis, however, remains sceptical. Many experiments have looked for particles travelling faster than light speed in the past and have come up empty-handed, he says. Most troubling for OPERA is a separate analysis of a pulse of neutrinos from a nearby supernova known as 1987a. If the speeds seen by OPERA were achievable by all neutrinos, then the pulse from the supernova would have shown up years earlier than the exploding star’s flash of light; instead, they arrived within hours of each other. “It’s difficult to reconcile with what OPERA is seeing,” Ellis says.
Ereditato says that he welcomes scepticism from outsiders, but adds that the researchers have been unable to find any other explanation for their remarkable result. “Whenever you are in these conditions, then you have to go to the community,” he says.
Dileep wrote: “yeah…go reformulate this. Something is not right and there’s probably some very large breakthrough lurking somewhere in the math. Maybe even a very powerful source of energy and materials understanding. To put it simply here are the major problems as I see them in the standard model: there isn’t even a tentative understanding of QM’s interaction with large-scale phenomena and while we were put off for a long time with ‘we’ll figure it out’, we have not. The state of the field is one of deeply researched fantasies that are not testable (superstring theory, or just string theory as advocated by Witten) and Quantum Loop Gravity, neither of which, as far as I can tell approach the realms of testable science. They seem answers only as far as they are supposition of themselves. So take that as problem 1. Problem 2: the detection of something we have called or decided to call two things, one a subject, dark matter and the other a phenomena, dark energy though their separation or possible Einsteinian co-equivalency may or may not be true. We don’t seem to understand if a) these things truly ‘exist’ or not (we have supposed them into existence since our math and measurement fall short). What are they? real? or simply holes in our models? Problem 3: the deeper we delve into the sublimely small (perhaps on the hunt for Mr. Witten’s strings, maybe not) we find more and more bizarreness but the manifold families of odd particles, quarks, bits of the above, etc, we are not finding the particles that may communicate forces such as gravity or a field particle. Space itself also seems to be less a certainty as we have held it and its expansion and shaping of the universe might be something entirely else.